inertia

The property of an object to resist changes to its state of motion. Being
an inherent property of mass, it is present
even in the absence of gravity. For example,
although a spacecraft may be located well away from any gravitating mass,
its inertia must still be overcome in order for it to speed up, slow down
or change direction. Inertia is a familiar concept in physics but its origin
is poorly understood. It is believed to be a property of bodies primarily
due to their interaction with masses at the edges of the universe. Momentum
(mass times velocity) is a measure of inertia; changes in momentum, resulting
from the action of an unbalanced force, permit a measure of inertial mass.